While that site and its links are nice references about wheat in general, as far as I can see, none of them specificially discuss the historical spread of durum wheat, which is what Wood is talking about. This page on the history of macaroni was the most thorough source I could find on the net about the arrival of durum in Italy. From what I can see, it agrees with her, at least as regards the Italian end of the issue. (I haven’t read it all; it contains far more about macaroni than someone who grew up in Seventies Scotland and to whom macaroni is indeliably glop out a can as a result could possibly want to know.) For the record, Wood isn’t pretending to be a food historian - she’s head of the Chinese collections in the British Library - and her reference is Claudia Roden’s The Food of Italy from 1989.
In her argument, by exactly the same means that other historians think he did: Rustichello was a good writer and the pair of them wrote an entertaining work, which was of great interest to their medieval contemporaries and successors. Where she differs is that she suggests that Marco had enough access to information about China from his father and uncle, who had gone at least once, and Arabic traders in the Black Sea region to pretend he’d been. As I’ve already indicated, I don’t find this overall thesis convincing. John Larner’s Marco Polo and the Discovery of the World (Yale, 1999) both argues against Wood (p60-3) and provides an excellent account of the reception and influence of Il Milione.